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EP0149461B1 - Traitement de surface de bandes d'acier électroplaquées d'un alliage de zinc - Google Patents

Traitement de surface de bandes d'acier électroplaquées d'un alliage de zinc Download PDF

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Publication number
EP0149461B1
EP0149461B1 EP19850100123 EP85100123A EP0149461B1 EP 0149461 B1 EP0149461 B1 EP 0149461B1 EP 19850100123 EP19850100123 EP 19850100123 EP 85100123 A EP85100123 A EP 85100123A EP 0149461 B1 EP0149461 B1 EP 0149461B1
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EP
European Patent Office
Prior art keywords
weight
parts
zinc
strip
zinc alloy
Prior art date
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Expired
Application number
EP19850100123
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German (de)
English (en)
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EP0149461A1 (fr
Inventor
Kazuma C/O Research Laboratories Yonezawa
Toshikuni C/O Research Laboratories Tanda
Hirotake C/O Research Laboratories Ishitobi
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JFE Steel Corp
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Kawasaki Steel Corp
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/82—After-treatment
    • C23C22/83—Chemical after-treatment
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/38—Chromatising
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
    • Y10T428/12556—Organic component
    • Y10T428/12569—Synthetic resin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12674—Ge- or Si-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12785—Group IIB metal-base component
    • Y10T428/12792—Zn-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
    • Y10T428/12826—Group VIB metal-base component
    • Y10T428/12847—Cr-base component
    • Y10T428/12854—Next to Co-, Fe-, or Ni-base component
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/31504—Composite [nonstructural laminate]
    • Y10T428/31678—Of metal
    • Y10T428/31688—Next to aldehyde or ketone condensation product

Definitions

  • This invention relates to the surface treatment of zinc alloy electroplated steel strips or sheets for outstandingly improving the corrosion resistance thereof and such treated zinc alloy electroplated steel strips.
  • the zinc alloy electroplated steel strips used herein designate composite zinc-plated steel strips, that is, steel strips having a zinc alloy layer electroplated thereon in which at least one metal is present in addition to zinc, including, for example, steel strips electroplated with Zn-Ni, Zn-Ni-Co, Zn-Ni-Cr, and Zn-Fe alloys.
  • zinc plating has long been used as a typical metal plating for improving the corrosion resistance of steel strips.
  • the zinc plating is to protect steel strips from corrosion by the sacrificial corrosion protection effect of zinc itself.
  • the amount of zinc deposited must be increased in order to enhance corrosion resistance. Increased amounts of zinc deposited, however, not only detract from the workability, weldability, and productivity of zinc plated steel, but also increase the cost.
  • One method for improving the corrosion resistance of such zinc electroplated steel strips is by incorporating an additional metal or metals into the zinc plating to produce zinc alloy plated steel strips. There are well known techniques for electroplating such alloys as Zn-Ni, Zn-Ni-Co, Zn-Ni-Cr, and Zn-Fe.
  • the alloy plating methods mentioned above are successful to some extent in that since the resulting zinc alloy platings form passivated films effective in retarding or preventing dissolution of zinc, the corrosion resistance of composite zinc plated steel strips is improved by a factor of about 3 to 5 over that of conventional zinc plated steel strips and thus allows the amount of composite zinc platings deposited to be reduced.
  • the composite zinc plated steel strips are still liable to formation of white rust and even red rust in relatively short time when they are allowed to stand indoors or outdoors and particularly when they are sprayed with water or salt water.
  • chromate treatment was also proposed to carry out a chromate treatment after single or composite zinc plating in order to further improve corrosion resistance.
  • the chromate treatment is effective, but not satisfactory to meet the needs of users in that white rust will appear after about 100 hours under high temperature and high humidity conditions and more under a salt-containing atmosphere.
  • an overcoat film by applying an aqueous solution comprising 100 parts by weight calculated as solids of a dispersion of a carboxylated polyethylene resin containing 3 to 20 mol% of carboxyl group, 10 to 30 parts by weight calculated as solids of a water-soluble melamine resin, and up to 10 parts by weight of a water-soluble chromium compound, and drying the applied film at a strip temperature of at least 130°C such that the sum of the coating weights of both the films is 0.3 to 4 g/m 2 .
  • an overcoat film by applying an aqueous solution comprising 100 parts by weight calculated as solids of a dispersion of a carboxylated polyethylene resin containing 3 to 20 mol% of carboxyl group, 10 to 60 parts by weight calculated as solids of colloidal silica, and optionally, up to 10 parts by weight of a water-soluble chromium compound, to such a thickness that the sum of the coating weights of the dried film and said chromate film is 0.8 to 4 g/m 2 .
  • an object of the present invention to provide a novel and improved method for the surface treatment of a zinc alloy electroplated steel strip for providing extra corrosion resistance.
  • the extra corrosion resistance used herein means that white rust does not form in surface-treated steel strips after about 500 hours and red rust does not form after about 1500 hours of salt water spraying.
  • a method for surface treating a zinc alloy electroplated steel strip for improving the corrosion resistance comprising the steps of
  • a zinc alloy electroplated steel strip having improved corrosion resistance comprising:
  • surface treated steel strips or sheets of this type are reguired to have excellent lacquer or paint adherence, spot weldability, solvent resistance, workability, and coating hardness as well as extra corrosion resistance.
  • the surface treated steel strips or sheets of the present invention meet all these requirements as will be later illustrated in Examples.
  • the zinc alloy layers electroplated on steel strips according to the present invention may preferably be alloys of zinc with at least one metal selected from nickel, cobalt, manganese, chromium, and iron. Other alloying metals will occur to those skilled in the art. Such a zinc alloy may be electroplated to a weight of at least 5 grams per square meter of steel surface.
  • Zinc-nickel alloy electroplated steel strips were treated in chromate solution so as to deposit varying amounts of chromium and then coated with a polyethylene resin composition. The coated strips were examined for corrosion resistance. The chromate treatment, resin coating, and corrosion test were carried out under the following conditions.
  • the starting steel strips are those having a thickness of 0.8 mm and electroplated with a zinc-nickel alloy (Ni 12.5%) to a weight of 20 grams per square meter (g/m 2 ).
  • the strips were coated with the chromate solutions of varying concentrations, squeezed by means of a flat rubber roll, and dried for 3 seconds with hot air at 85°C.
  • the resulting chromate films contained chromium in the range of 1.5 to 96 mg/m 2 .
  • the steel strips chromated in (1) were coated with an aqueous composition which contained 100 parts by weight of a dispersion of a polyethylene resin having 10 mol% of carboxyl groups, 15 parts by weight of a water soluble melamine resin, and 20 parts by weight of colloidal silica, all the parts by weight being based on the solids of the respective components.
  • the coated strips were then squeezed by means of a roll and dried for 30 seconds with hot air at 150°C.
  • the resulting resin coatings all had a weight of 2.0 g/m 2 .
  • the corrosion test was carried out according to the procedure of salt spray test JIS Z 2371. The percent formation of red rust was determined after the test period of 1500 hours of spraying of 5% salt water.
  • the chromate solution for providing an undercoating is mainly composed of chromic anhydride (Cr0 3 ) and may contain, for example, etching and accelerating agents in the form of sulfuric acid or sulfates, phosphoric acid or phosphates, hydrofluoric acid or fluorides, boric acid, salt (sodium chloride), and the like.
  • the chromate solution may be either of the reaction type or of the coating type as long as they can yield a chromate film mainly composed of hydrated chromium oxides in a weight of 2 to 60 mg/m 2 of chromium.
  • Chromium weights of less than 2 mg/m 2 are insufficient to provide corrosion resistance whereas the appearance of products is impaired at chromium weights of more than 60 mg/m 2 due to non-uniform coating thickness and inconsistent color tone.
  • the chromate solution may be applied by any well-known techniques including spraying, dipping, and roll coating followed by squeezing with a roll or air knife, and then by hot air drying.
  • the coating composition which may be used to form a polyethylene resin overcoating is comprised of a carboxylated polyethylene resin dispersion, a melamine resin, and colloidal silica as mentioned above.
  • the polyethylene resins used herein are those polyethylene resins having 3 to 20 mol% of carboxyl groups attached thereto. Although ethylene-vinyl acetate emulsions and polyethylene waxes are generally included in polyethylene resins, they result in less corrosion resistant coatings. No water-soluble polyethylene resit) is available at present. Carboxylated-polyethylene resins have besn found optimum for the present invention.
  • Polyethylene resins having less than 3 mol% of carboxyl groups cannot be fully emulsion polymerized and thus result in less adherent coatings whereas polyethylene resins having more than 20 mol% of carboxyl groups result in coatings which are deteriorated in such properties as corrosion resistance.
  • the polyethylene resins used herein may be either homopolymers or copolymers.
  • the water-soluble melamine resin is used as a crosslinking agent in amounts of 10 to 30 parts by weight per 100 parts by weight of the solids of the carboxylated polyethylene resin dispersion. Good coating hardness and solvent resistance are not achieved with less than 10 parts by weight of the melamine resin. More than 30 parts weight of the melamine resin causes the composition to be gelled to reduce its pot life and adversely affects the corrosion resistance of the resulting coatings.
  • the crosslinking melamine resins are thermosetting melamine-formaldehyde resins such as methylol melamine resins which are commercially available from various manufacturers.
  • the colloidal silica is used in amounts of 10 to 60 parts per 100 parts by weight of the solids of the carboxylated polyethylene resin dispersion.
  • the colloidal siJica is included in order to improve the hardness and corrosion resistance of coatings. Less than 10 parts by weight of colloidal silica fails to provide sufficient coating hardness whereas more than 60 parts by weight adversely affects the corrosion resistance and paint adherence.
  • the colloidal silica used herein is also commercially available in aqueous dispersion form.
  • the polyethylene based coating should preferably have a weight in the range of 0.3 to 5 g/ M 2 . Coatings of less than 0.3 g/m 2 are too thin to provide good corrosion resistance. Coatings of more than 5 g/m 2 provide good corrosion resistance, but disturb spot welding.
  • the composition may be applied to steel strips by any well-known techniques including roll coating and dipping/grooved roll squeezing.
  • the composition may be adjusted to any desired concentration depending on the particular coating technique employed.
  • the applied composition is then dried into a coating with hot air while the underlying strip should be heated to a temperature of at least 130°C. Heat is applied for evaporating off the water and crosslinking the resins.
  • the coating does not harden to a sufficient hardness at strip temperatures of less than 130°C. Increasing the strip temperature more than necessary is not economically desirable.
  • a steel strip which had been electroplated with a zinc-nickel alloy (Ni 12.5 wt%) to a weight of 20 g/m 2 was spray coated with an undercoating chromate solution containing 20 grams/liter of CrO 3 and 4 grams/liter of Na 3 AIF 6 , squeezed by means of a flat rubber roll, and dried with hot air.
  • the weight of chromium deposited was 20 g/ M 2 .
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of a dispersion of a carboxylated polyethylene resin containing 12 mol% of carboxyl groups, 15 parts by weight of a water-soluble melamine resin, and 20 parts by weight of colloidal silica, all the parts by weight being based on the solids of the respective components.
  • a resin coating having a weight of 2.5 g/m 2 was obtained by drying the applied composition at a strip temperature of 135°C.
  • a steel strip which had been electroplated with a zinc-nickel alloy (Ni 12.5 wt%) to a weight of 20 g/m 2 was spray coated with an undercoating chromate solution containing 10 grams/liter of Cr0 3 and 2 grams/litter of Na 3 AIF 6 , squeezed by means of a flat rubber roll, and dried with hot air.
  • the weight of chromium deposited was 16 mg/m 2 .
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of the same carboxylated-polyethylene resin dispersion as used in Example 1, 20 parts by weight of a water-soluble melamine resin, and 30 parts by weight of colloidal silica, all the parts by weight being based on the solids of the respective components.
  • a resin coating having a weight of 1.8 g/m 2 was obtained by drying the applied composition at a strip temperature of 140°C.
  • a steel strip which had been electroplated with a zinc-nickel alloy (Ni 12.5 wt%) to a weight of 20 g/m 2 was spray coated with an undercoating chromate solution containing 10 grams/liter of Cr0 3 , 2 grams/liter of Na 3 AIF 6 , and 40 grams/liter of colloidal silica and then squeezed and dried in the same manner as in Example 1.
  • the weight of chromium deposited was 10 mg/m 2.
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of a dispersion of a carboxylated-polyethylene resin containing 10 mol% of carboxyl groups, 16 parts by weight of a water-soluble melamine resin, and 15 parts by weight of colloidal silica, all the parts by weight being based on the solids of the respective components.
  • a resin coating having a weight of 3.8 g/m 2 was obtained by drying the applied composition at a strip temperature of 150°C.
  • This example illustrates the control, that is, the zinc-nickel alloy electroplated steel strip having a plating weight of 20 g/m 2 as used in Example 1.
  • This example illustrates the steel sample which was coated with a chromate film after zinc-nickel alloy plating in Example 1. That is, a zinc-nickel alloy electroplated steel strip was spray coated with an undercoating chromate solution containing 20 grams/liter of Cr0 3 and 4 grams/liter of Na 3 AIF 6 , squeezed by means of a flat rubber roll, and dried with hot air. The weight of chromium deposited was 20 mg/m 2 .
  • the steel sample of Comparative Example 2 was further coated with an aqueous composition containing 12% by weight of a polyacrylic acid, which was dried into a coating of 2.5 g/m 2 .
  • a salt spray test was carried out according to JIS Z 2371. The percent formation of rust was determined at the end of the test period.
  • the hardness of the resinous coating was expressed in pencil hardness.
  • a continuous welding test was carried out by using a stationary spot welding machine and repeating spot weldings until the nugget diameter reached 4 mm.
  • a melamine alkyd resin type paint was applied to samples and baked at 150°C for 30 minutes into a paint film of 25 p m thick.
  • the paint film was scribed and an Erichsen test was carried out by extruding the scribed sample by 7 mm. The sample was examined whether the paint film sections were peeled.
  • a rubbing test was carried out by rubbing the sample surface with cotton impregnated with methylene chloride.
  • a scribing peel test using a Scotch adhesive tape and a zero T-bend test were carried out.
  • a steel strip which had been electroplated with zinc to a weight of 20 g/m 2 was spray coated with an undercoating chromate solution containing 10 grams/liter of Cr0 3 and 2 grams/liter of H 2 SiF 6 , squeezed by means of a flat rubber roll, and dried with hot air.
  • the weight of chromium deposited was 40 mg/m 2 .
  • This chromate treated strip was dipped in an aqueous composition composed of 10 wt% of a carboxylated polyethylene resin and 0.6 wt% of chromic anhydride. An overcoat having a weight of 1.4 g/m 2 was obtained after drying at 150°C.
  • a steel strip which had been electroplated with zinc to a weight of 20 g/m 2 was spray coated with an undercoating chromate solution containing 10 grams/liter of Cr0 3 and 2 grams/liter of H 2 SiF 6 , squeezed by means of a flat rubber roll, and dried with hot air.
  • the weight of chromium deposited was 28 mg/m 2 .
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of a dispersion of a carboxylated-polyethylene resin containing 10 mol% of carboxyl groups, 15 parts by weight of a water-soluble melamine resin, and 5 parts by weight of ammonium chromate, the parts by weight of the former two components being based on their solids.
  • a resin coating having a weight of 1.6 g/m 2 was obtained after drying at 135°C.
  • a steel strip which had been electroplated with zinc to a weight of 20 g/m 2 was spray coated with an undercoating chromate solution containing 10 grams/liter of CrO 3 and 2 grams/liter of H 2 SiF 6 , squeezed by means of a flat rubber roll, and dried with hot air.
  • the weight of chromium deposited was 38 mg/m 2 .
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of a dispersion of a carboxylated-polyethylene resin containing 10 mol% of carboxyl groups, 30 parts by weight of colloidal silica, and 3 parts by weight of ammonium chromate, the parts by weight of the former two components being based on their solids.
  • a resin coating having a weight of 1.7 g/m 2 was obtained after drying at 145°C.
  • This example illustrates the coating of a Zn plated steel strip with a coating composition according to the present invention.
  • a steel strip which had been electroplated with zinc to a weight of 20 g/m 2 was spray coated with an undercoating chromate solution containing 10 grams/liter of CrO 3 and 2 grams/liter of H 2 SiF 6 , squeezed by means of a flat rubber roll, and dried with hot air.
  • the weight of chromium deposited was 38 mg/m 2 .
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of a dispersion of a carboxylated-polyethylene resin containing 12 mol% of carboxyl groups, 15 parts by weight of a water-soluble melamine resin, and 20 parts by weight of colloidal silica, all the parts by weight being based on the solids of the respective components.
  • a resin coating having a weight of 1.0 g/m 2 was obtained by drying the applied composition at a strip temperature of 140°C.
  • the data for Comparative Examples 1 and 2 shows that the zinc alloy plating and the chromate film as exposed do not protect steel from rust.
  • the data for Comparative Example 3 shows that a coat of ' polyacrylic acid is less rust preventive on zinc alloy plated steel with a chromate film.
  • the data for Comparative Examples 4, 5, and 6 shows that although the previously proposed coating compositions are satisfactorily rust preventive on zinc plated steel strips in a 200 hour salt spray test, they are not satisfactory in an extended (500 hour) salt spray test.
  • the data for Comparative Example 7 shows taht the coating composition of the present invention is not fully satisfactory in rust prevention when applied to zinc plated steel strips.
  • the coating composition of the present invention is fully effective in rust protection only when applied to zinc alloy plated steel via a chromate film.
  • a steel strip which had been electroplated with a zinc-manganese alloy (Mn 21.0 wt%) to a weight of 30 g/m 2 was spray coated with an undercoating chromate solution containing 20 grams/liter of Cr0 3 , 2 grams/liter of Na 3 AlF 6 , and 40 grams/liter of colloidal silica, squeezed by means of a fluted rubber roll, and dried with hot air.
  • the weight of chromium deposited was 50 mg/m 2.
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of a dispersion of a carboxylated-polyethylene resin containing 12 mol% of carboxyl groups, 20 parts by weight of a water-soluble melamine resin, and 20 parts by weight of colloidal silica, all the parts by weight being based on the solids of the respective components.
  • a resin coating having a weight of 2.1 g/m 2 was obtained by drying the applied composition at a strip temperature of 140°C.
  • a steel strip which had been electroplated with a zinc-cobalt alloy (Co 5.0 wt%) to a weight of 30 g/m 2 was spray coated with an undercoating chromate solution containing 20 grams/liter of Cr0 3 , 3 grams/liter of Na a AIF 6' and 30 grams/liter of colloidal silica, squeezed by means of a flat rubber roll, and dried with hot air.
  • the weight of chromium deposited was 45 mg/m 2.
  • This chromate treated strip was further coated with an aqueous composition composed of 100 parts by weight of a dispersion of a carboxylated polyethylene resin containing 12 mol% of carboxyl groups, 15 parts by weight of a water-soluble melamine resin, and 20 parts by weight of colloidal silica, all the parts by weight being based on the solids of the respective components.
  • a resin coating having a weight of 2.3 g/m 2 was obtained by drying the applied composition at a strip temperature of 140°C.
  • the present invention provides surface coated steel strips which not only meet the extra corrosion resistance required particularly for steel strips useful in the manufacture of automobiles and electric appliances, but also exhibit excellent spot weldability, paint adhesion and solvent resistance. It is also demonstrated that the present invention is equally applicable to steel strips having any zinc alloys electroplated including zinc-mangahese and zinc-cobalt alloys as well as zinc-nickel alloy.

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  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
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  • Application Of Or Painting With Fluid Materials (AREA)
  • Laminated Bodies (AREA)
  • Chemical Treatment Of Metals (AREA)

Claims (5)

1. Une méthode de traitement de surface d'une bande d'acier électroplaquée avec un alliage de zinc, pour améliorer le résistance à la corrosion, comprenant les étapes consistant à:
former zur la feuille d'acier électroplaquée avec un alliage de zinc, un film de chromate ayant du poids de 2 à 60 mg/m2 de chrome, et
à appliquer à la feuille traitée au chromate une composition aqueuse comprenant 100 parties en poids d'une dispersion d'une résine de polyéthylène carboxylé ayant 3 à 20 mole% de groupements carboxyliques, 10 à 30 parties en poids d'une résine hydrosoluble de mélamine, et 10 à 60% en piods de silice colloïdale, toutes les parties en poids étant calculée par rapport à la teneur en solides des constituants respectifs, puis à sécher la composition sur la feuille à une température de feuille d'au moins 130°C pour former un revêtement résinaux ayant un poids de 0,3 à 5 g/m2..
2. Méthode selon la revendication 1, dans laquelle l'alliage de zinc est choisi parmi les alliages du zinc avec au moins un métal choisi parmi le nickel, le manganèse, le cobalt, le chrome et le fer.
3. Méthode selon la revendication 1, dans laquelle le film de chromate est formé par application d'une solution de chromate à la feuille électroplaquée, suivie d'un séchage.
4. Une feuille d'acier électroplaquée avec un alliage de zinc, ayant des propriétés améliorées de résistance à la corrosion, comprenant
une feuille d'acier,
une couche d'alliage de zinc électroplaquée sur la feuille,
un film de chromate formé sur la couche d'alliage de zinc et ayant un poids de 2 à 60 mg/m2, et
un revêtement durci, sur le film de chromate, comprenant 100 parties en poids d'une résine de polyéthylène ayant 3 à 20 mole% de groupements carboxyliques, 10 à 30 parties en poids d'une résine hydrosoluble de mélamine, et 10 à 60% en poids de silice colloïdale, et ayant un poids de 0,3 à 5 g/m2.
5. Feuille selon la revendication 4, dans laquelle l'alliage de zinc est choisi parmi les alliages du zinc avec au moins un métal choisi parmi le nickel, le manganèse, le cobalt, le chrome et le fer.
EP19850100123 1984-01-17 1985-01-08 Traitement de surface de bandes d'acier électroplaquées d'un alliage de zinc Expired EP0149461B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP6061/84 1984-01-17
JP59006061A JPS60149786A (ja) 1984-01-17 1984-01-17 耐食性に優れた亜鉛系合金電気めつき鋼板の表面処理方法

Publications (2)

Publication Number Publication Date
EP0149461A1 EP0149461A1 (fr) 1985-07-24
EP0149461B1 true EP0149461B1 (fr) 1988-06-29

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US4548868A (en) 1985-10-22
JPS60149786A (ja) 1985-08-07
EP0149461A1 (fr) 1985-07-24
DE3563545D1 (en) 1988-08-04
JPH0144387B2 (fr) 1989-09-27

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